System of radio communication.



G. W. PICKARD.'

SYSTEM OF RA DIO COMMUNICATION. APPLICATION men ocnzs. 1914.

1 206,91 1 Patented Dec; 5, 1916.

GweMW/waw g h g Atty STATES PATENT OFFICE.

GREENLEAF WHITTIER PICKARD, OF AMESBURY, MASSACHUSETTS, ASSIGNOB, TO WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A

SYSTEM OF RADIO COMMUNICATION.

Specification of Letters Patent.

Patented Dec. 5, 1916.

Application filed October 28, 1914. Serial No. 869,089.

To all-whom it may concern.-

Be it known that I, GREENLEAF WHITTIER PIGKARI), a citizen ofthe United States of America, and a. resident :Qf Amesbury, Massachusetts, h ave invented new and useful Improvements in Systems of Radio Communication,- the principles of which are set forth in the following specification and accompanyingdrawings, which disclose thement, and a system whichis without energy limitation and therefore adapted for any desired power; also a system having an arrangement of receiving apparatus suitable for coiiperation with such a transmitter.

More specifically, the objects of the invention comprise that of having such difference between the periods of the antenna and the circuit supplying energy thereto that the.

radiation of energy will be prolonged as compared with radiation from the same antenna alone, more particularly when the osclllatlon-producing circuit is so constructed and arranged that such prolongation is prevented from deleterious reaction on the osdilation-producing circuit.

The drawing is a diagrammatic illustration of an embodiment of the invention in a form which has been demonstrated .to accomplish said ob ects under commercial conditions.

F is a suitable alternating current generator, and T a step-up transformer for the same, connected to supply energy to the oscillation -producing circuit which includes spark gap G, the condensers C, K and the inductance A. EGap G comprises five units of any suitable'quenched gap construction, with an approximate voltage of 8,000 at 500 cycles when generator F is an ordinary 500 cycle machine such as has beenthe standard practicefor many years.- (A generator of any other frequency may be employed, ifdesired, with a corresponding modification of the design of the other apparatus.) Condenser C has a capacity of .005 microfarads and condenser K .012 microfarads, the latter servlng to link the oscillation-producing circuit or exciter t0 the energy-storage circuit or reservoir K,.D, B, condenser D of which has a capacity.of .00l5 microfarads and serves to link the reservoir circuit to the radiator circuitv E, D, H. Inductances A and B of the two closed circuits'are variable and have suilicient inductance to permit the proper relative adjustments of their circuits to cause an efiicient transfer of energy from the exciter to the reservoir.

'1 The radiator has a capacity which is substantially that of condenser D, 6. about .0015 microfarads; it has an inductance of 26-microhenries, and a resistance varying from 6 to 14 ohms. The reservoir K, B, D has a wave-length of 4:22 meters, 2'. 6., the same as that of the radiated waves, the radiator having no period approximating that of the reservoir circuit, in the case being described having a natural period of 250 meters. I

With an energy supply of 1000 watts in the primary transformer T, the radiation obtained is 800 watts, i. e., an efficiency of 80 per cent. The radiated wave is pure and free from bumps and has low decrement. Similar results accompany the employment of a like arrangement wherein condensers K and D are replaced by oscillation-transformers for linking the respective circuits, but the condenser-linking shown is preferred;

A very important feature is theemployment of spark gap. G in a form .which will constitute the oscillation-producing circuit an impact exciter, i. 0. wherein the oscillations, forthwith upon t e transfer of energy to the reservoir, are quenched or extinguished in the exciter circuit, so that the reservoir is left operatively free of the exciter, to oscillate independently thereof. Such spark gaps are of well known construction, having been 'employed in other arrangements, and being usually provided with a blower to assist the multi-disk construction in rapidly cooling the gap. The construction G, diagrammatically indicates any such known complete means for sparkproduction'and quenching. This quenching action is important in the combination hereof, because the resulting operative independence of exciter and reservoir, after quenching, and the prevention, after the energy transfer, of reaction by the reservoir back on the exciter, causes the production of-oscillations which-are pure and uniform and of a single frequency, and causes a maximum proportion of the energy which is supplied to the system to be passed along to the radiator, and causes the only possible outlet for the energy transferred from exciter to reservoir, to be the radiator whence this energy is usefully employed in the radiation, which isthe only object of the transmitter. The most important feature of this quenching exciter, however, is in connection with the out-of-tune relation of the reservoir and radiator. Since the reservoir is constructed, as described, to have small losses by resistance or otherwise, 'theenergy stored therein will continue to oscillate therein until drawn away by the radiator. Since the only outlet to this stored energy is the radiator (the energy being prevented,

by the quenching exciter, from returning to the latter), therefore the relation to each other of the respective periods of the reservoir and radiator affects only the rate at which the energy istransferred from reser voir to radiator. It is desirable to decrease the damping-of radiation, and to prolong and increase thev persistence of radiation, and this is done in this invention by transferring the energy from the reservoir to the radiator at a low rate, by the provision of the radiator as herein described, of a period materially lower than that of the reservoir, (nearly one half in the specific case described.) The radiator, therefore, usefully serves to hold the energy back in the reservoir (as distinguished from too-rapidly completed radiation from an antenna of the construction disclosed, if used without such reservoir), and this is permitted in this invention without any result of forcing a' deleterious reaction of the reservoir on the exciter, by means of the quenched gap construction of the spark gap in the exciter circuit. However, if the criterion of a given installation be that low period of the radiator, which thereby exerts a maximum useful" effect in delaying the transfer of energy from the reservoir to-the radiator, then the spark gap G is constructed as an adequate quenching means, so as to insure against any reaction of the reservoir back on the exciter, which might otherwise result from said action 'of'the radiator in partially holding back the energy in the reservoir. The length of the radiated waves is.

determined by the period of the reservoir, which in turn is determined by the adjustment of coils B therein. The radiator, in addition to its expressed function of radiating, here has the additional function of-cooperating with the reservoirto prolong the period of radiation ofenergy. I have demonstrated that this action, consisting in prolonging the transfer from reservoir to radiator, is so usefulthat a high degree of radiation efiiciency is present when the period of the reservoir is several times'that of the radiator;'this being true, however. only when the quenching means J G has suchquenching efliciency as to prevent material reaction on the exciter by the energy which is held in the reservoir by the radiator. It is also extremely important, for maximum radiation efiiciency, in proportion to the degree of perfection of the quenching means, that the exciter and reservoir be accurately adjusted relative .to each other, as by the inductances A, B, so as to cause the maximum transfer of energy to the reser- .voir in the minimum time of operation of the exciter, before the cessation of the activity of the exciter due to the quenching of the spark.

The receiver diagrammaticallv illustrated is suitable for cooperation with the above transmitter. This receiver is that of my Patent 876,996, for magnetic loop antenna, giving maximum efficiency when in line with the radiation from the transmitter. The magnetic loop L is a closed circuit, thereby tending to prevent re-radiation of the received energy, and conserving the energy for use by the local receiving apparatus. By means of variable capacity D the receiving loop L may be sharply tuned to the transmitted waves.

Detector G, in shunt to condenser D, i

may be of any suitable type, such as the mineral rectifier, and its. circuit has no period approximating that of loop L. It is preferable thus to dispense, at the receiver.

with any circuit between the receiving loop and the detector circuit, such asthe reservoir at the transmitter, because such a circuit would increase the tendency to re-radiation-of the received energy.

In the arrangement shown, condenser U is repeatedly charged from detector G'as this-condenser discharges through the coil of the telephone T, condenser U being adjustable, and typifying-any suitable'means' cooperating with the inductance of the telephone coils for tuning the telephone circuit to the train-frequency of the transmitted waves. Suchtrain-frequency is made to correspond as closely as possible with the mechanical period of the diaphragmof telephone T' (about 1000 per second) by'the use of the 500 cycle generator at the generator above specified; or, if a enerator of different frequency is employed, y selecting a diaphragm for the telephone which shall have a period which corresponds as closely as possible with the period of the'generator employed. The sharper this mechanical tuning, and the sharper the electrical tuninto mechanical motion of the telephone diaphragm. In this receiver, when used with described transmitter, three features contribute to the efficient reception, retention and utilization of the energy of the waves radiated from the transmitter,- i. 6., first, the employment of the closed receiving antenna; second, the direct connection of the detector-telephone circuit to the receiving antenna, without the interposition of any reservoir or other tuned circuit; and third, wave-train tuning, by the employmentof transmitter-generator and telephone diaphragm of as nearlythe same period as possible, and by the employment of means for electrically tuning the circuit of the telephone-winding to the. period of such generaton. All of thesefeatures of the re- 4 ceiver are preferably employed with the transmitter hereof, althou h the train-tuning may be obtained by eit er the -mechani-.

cal or the electrical means alone, and although the transmitter may be employed, if desired, with any operative receiver.

I claim 1. In 'a transmitter of electromagnetic waves, the combination with an exciter, of

a reservoir adjusted thereto and charged thereby, and a radiator having a substantially shorter period than the reservoir,-and

thereby prolonging theaction of the latter; said exciter being of the quenching impact type,'-and thereby preventing reaction on the exciter by energy held back in the'reservoir by the radiator, substantially as and for the purpose described.

' 2.. In a transmitter of electromagnetic Waves, the combination with an exciter, of areservoir having a period which is that of the radiated waves, and a radiator having a substantially shorter period than that of the reservoir and waves, and thereby prolonging the action of the reservoir and consequent wave-radiation; said exciter being of the quenching impact type and thereby preventing reaction on the exciter by the radiator and reservoir, substantially as and for the purpose described.

3. In a transmitter of electromagnetic.

waves, the combination with a quenching impact-exciter, of a reservoir linked thereto by a condenser, and a radiator linked to the reservoir b a condenser, and having a substantially s iorter period than the reservoir. 4. In a transmitter of electromagnetic waves, the combination with a quenching impact-exciter, of a reservoir-linked thereto by' a condenser, and radiator having a substantially shorter period than the reservoir.

5. In a transmitter of electromagnetic waves, the combination with a quenching impact-exciter, of a reservoir having the same period as that of the transmitted waves, and a radiator linked to the reservoir by a condenser and having a substantially shorter period than the reservoir.

6. In a transmitter of electromagnetic waves, the combination with a quenching impact-exciter, of a reservoir linked thereto by a condenser, anda radiator linked to the reservoir by a condenser.

GREENLEAF WHITTIER PIGKARD.

Witnesses: WILLIAM J. BARKLEY,

J. ALBERT Pnoc'ron. 

